There have been many types and kinds of electro-mechanical locks and locking mechanisms used to protect valuables. For example, reference may be made to the following U.S. Pat. Nos.: 3,475,061; 3,710,136; 4,019,355; 4,148,092; 4,457,148; 4,493,001; 4,514,731; 4,762,212; 4,754,625; 4,770,012; 4,831,851; 4,838,052; 4,926,664; and 5,437,174.
As disclosed in the foregoing mentioned patents various lock mechanisms are battery powered and include circuitry for detecting when the power of an associated battery falls below a predetermined level. For example, U.S. Pat. Nos. 4,148,092 discloses an battery powered electronic combination door lock having a voltage detection circuit that causes an alarm to be sounded when the voltage of the battery falls below a predetermined level.
While such electro-mechanical locks may have been satisfactory for some applications, it would be highly desirable to have a new and improved electro-mechanical lock which provides an indication of a low battery voltage condition and which facilitates battery replacement when the battery voltage falls below a predetermined level.
U.S. Pat. No. 4,493,001 disclose a battery rundown protection system wherein the low voltage battery condition is detected before it become so low as to not be suitable for device actuation. In this regard, when the battery voltage falls below a predetermined level, the battery is temporarily disconnected from its load and then subsequently connected to the load when a user attempts to utilize the device.
While such a system provides the user with an indication of a low battery voltage condition and enables the user to gain device access under such low voltage conditions, the disclosed system does not facilitate battery replacement when the battery voltage falls below the predetermined level. In this regard, if the user continues to access the device under such low voltage conditions, the repeated entries would eventually cause the battery to reach a level that would preclude a successful entry.
For example, if an electronic combination door lock, such as disclosed in U.S. Pat. No. 4,148,092 included such a battery rundown protection system, each user of the door lock would become aware of the low voltage condition as he or she accessed the door lock, but such access would not encourage the user to seek replacement of the battery as access is still achieved in the low battery voltage condition. Thus, where an electronic lock has many users seeking access, such repeated use in a low battery voltage condition would eventually cause the battery to reach a level where entry was precluded.
Therefore, it would be highly desirable to have a new and improved battery powered electro-mechanical lock, which can be readily utilized during low battery voltage conditions but which also facilitates battery replacement when the low voltage condition is detected.